Patent document 1 discloses filter cartridges serving as membrane components that house cylindrical filter main bodies. These filter cartridges include filter cases, which serve as membrane casings. The filter cases are constituted of cylindrical filter-case main bodies that house the filter main bodies, and filter-case lid bodies that can be screwed to threaded portions formed on the inner peripheries of edges of the filter-case main bodies.
These membrane components are configured so that predetermined regions of the filter main bodies will be positionally secured by seal members in a watertight manner by tightening, after the filter main bodies with the seal members disposed on the tops and the bottoms of the filter main bodies are put in the filter-case main bodies, the filter-case lid bodies that can be screwed to the filter-case main bodies.